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NASA NTRS1993

Locating Electron Traps In A CCD

"Pocket pumping" is technique for mapping sizes of electron-trapping defects and picture elements within which traps located in charge-coupled device (CCD). Two kinds of traps: forward and reverse. Pocket pumping relies on fact that in terms of charges measurable by external circuitry, forward traps affect only forward, while reverse traps affect only reverse, transfer of charge along row or column of picture elements. Charges in picture elements shifted back and forth many times to amplify trapping effect by repetition. Traps smaller than 1 electron detected by this method.

Janesick, James↗

NASA NTRS1989

Metal Film Increases CCD Quantum Efficiency

Thin layer of platinum or other high-work-function metal applied to back side of rear-illuminated charge-coupled device (CCD) achieves quantum efficiency (QE)-pinned state, an ideal condition allowing sensor to achieve 100-percent internal charge-collection efficiency within its photosensitive volume. Metal layer, called flash gate, easily applied by tungsten vacuum deposition during last step of sensor fabrication.

Janesick, James R.↗

NASA NTRS1994

Monolithic in-based III-V compound semiconductor focal plane array cell with single stage CCD output

A monolithic semiconductor imager includes an indium-based III-V compound semiconductor monolithic active layer of a first conductivity type, an array of plural focal plane cells on the active layer, each of the focal plane cells including a photogate over a top surface of the active layer, a readout circuit dedicated to the focal plane cell including plural transistors formed monolithically with the monolithic active layer and a single-stage charge coupled device formed monolithically with the active layer between the photogate and the readout circuit for transferring photo-generated charge accumulated beneath the photogate during an integration period to the readout circuit. The photogate includes thin epitaxial semiconductor layer of a second conductivity type overlying the active layer and an aperture electrode overlying a peripheral portion of the thin epitaxial semiconductor layer, the aperture electrode being connectable to a photogate bias voltage.

Fossum, Eric R.↗

NASA NTRS1995

Monolithic in-based III-V compound semiconductor focal plane array cell with single stage CCD output

Fossum, Eric R.↗

DOE OSTI2026

In situ cryogenic characterization of proton damage in thick p-channel skipper CCDs

Skipper charge-coupled devices (CCDs) are an offshoot of standard silicon pixel detectors and are capable of performing repeated non-destructive charge measurements, enabling deeply sub-electron readout noise. This capability has opened the door to single-photon counting from the near-infrared ($\sim$1.1 $μ$m) to the soft X-ray (several keV), making these devices strong candidates for future astronomical instruments operating in the photon-starved limit. Furthermore, the p-channel architecture used to fabricate Skipper CCDs on n-type silicon has been demonstrated to have an increased hardness to the intense radiation environment of space. Building upon previous irradiation campaigns on room-temperature sensors, here we describe the first radiation-hardness tests of p-channel skipper CCDs at their cryogenic operating temperatures. We assess the performance of the floating-gate output stage and global CCD parameters (charge transfer inefficiency, dark current, hot pixels, and charge traps). We find that these devices maintain excellent performance after displacement damage doses equivalent to ${\sim}$10 years at the Earth/Sun L2 Lagrange point, demonstrating for the first time that these sensors remain radiation-hard in realistic deep-space thermal and radiation environments.

Roach, Brandon M. [Chicago U., KICP] (ORCID:000000↗

DOE OSTI2020

Smart-readout of the Skipper-CCD: Achieving Sub-electron Noise Levels in Regions of Interest

The skipper CCD is a special type of charge coupled device in which the readout noise can be reduced to sub-electron levels by averaging independent measurements of the same charge. Thus the charge in the pixels can be determined by counting the exact number of electrons. The total readout time is proportional to the number of measurements of the charge in each pixel. For some applications this time may be too long; however, researchers usually are interested only on certain region within the matrix of pixels. In this paper we present the development of a smart skipper readout technique that allows the user to specify regions of interest of the CCD matrix where an arbitrary (high) number of measurements of the same charge can taken to obtain the desired noise level, and far less measurements are performed in those regions that are less interesting to the researcher, therefore reducing the total readout time.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

NASA NTRS1993

Photodetector Array For Neural Network

Integrated circuit performs 1,024 threshold operations in parallel. Designed for use in postprocessing output of optical correlator in optoelectronic neural network. Overall function of device to put out digital signals indicative of location(s) of bright spot(s) on detector plane. Response time less than commercial charge-coupled-device (CCD) imaging detector operating at standard television frame rate.

Langenbacher, Harry↗

DOE OSTI2026

MAS-CCD: New technique for measuring low-level charge content based on the multiple amplifier architecture

Low-noise detectors are a key technology for the next generation of astronomical instruments aimed at spectroscopy of faint objects and the search for exoplanets. In this context, the multiple-amplifier sensing charge-coupled device (MAS-CCD) emerges as a promising technology for future scientific instruments. A critical parameter affecting the performance of these devices is spurious charge, produced by the clocking of the gates. Its measurement is typically challenging with existing methods. In practice, the optimization of this parameter often relies on empirical procedures that require significant time and careful consideration of the trade-off with full-well capacity. In this work, we present a new technique to estimate spurious charge based on covariance analysis of the output amplifiers of the MAS-CCD, which measures the same charge packet in different amplifiers at different times. The method enables fast and precise measurements of spurious charge under operating conditions where conventional approaches are difficult to apply. We develop the theoretical framework of the method and validate the model through simulations. The results demonstrate the feasibility of this approach and suggest that it could serve as a basis for reliable large-scale characterization of sensor performance.

Gamero, Miqueas E. [Buenos Aires, CONICET; Fermila↗

NASA NTRS2003

MOS Circuitry Would Detect Low-Energy Charged Particles

Metal oxide semiconductor (MOS) circuits for measuring spatially varying intensities of beams of low-energy charged particles have been developed. These circuits are intended especially for use in measuring fluxes of ions with spatial resolution along the focal planes of mass spectrometers. Unlike prior mass spectrometer focal-plane detectors, these MOS circuits would not be based on ion-induced generation of electrons, and photons; instead, they would be based on direct detection of the electric charges of the ions. Hence, there would be no need for microchannel plates (for ion-to-electron conversion), phosphors (for electron-to-photon conversion), and photodetectors (for final detection) -- components that degrade spatial resolution and contribute to complexity and size. The developmental circuits are based on linear arrays of charge-coupled devices (CCDs) with associated readout circuitry (see figure). They resemble linear CCD photodetector arrays, except that instead of a photodetector, each pixel contains a capacitive charge sensor. The capacitor in each sensor comprises two electrodes (typically made of aluminum) separated by a layer of insulating material. The exposed electrode captures ions and accumulates their electric charges during signal-integration periods.

Sinha, Mahadeva↗

NASA NTRS1981

Planetary exploration sensor systems

Most of the instruments that have been used in planetary exploration have been either spectrometers or imaging devices. Instruments of these types are being developed for the Galileo and VOIR (Venus Orbiting Imaging Radar) missions. Galileo will take advantage of new CCD (charge-coupled device) technology, and VOIR will use techniques of synthetic aperture radar developed for Seasat. For determining the macrostructure of mineral resources, the best approach is believed to involve acoustic imaging, essentially a seismic data processing technique. Determinations of microstructure would require a light microscope and an electron microscope. For determining the nature and form of volatiles, a differential scanning calorimeter could be used. To determine the mineral composition, an electron beam microprobe with X-ray fluorescence and spectroscopy would be used.

Saunders, R. S.↗

DOE OSTI2021

Sub-GeV dark matter and neutrino searches with Skipper-CCDs: status and prospects

Thick fully-depleted charge-coupled devices (CCDs) with high-resistivity silicon are used in a wide range of scientific applications, from particle detection to astronomical imaging. Their low noise and high charge collection efficiency allow us to reach unprecedented sensitivity to physical processes with low-energy transfers. The newly-developed Skipper-CCD enhances this sensitivity by reducing the read-out noise reaching a sub-electron resolution. In this work, we summarize the fundamentals of the skipper-CCD operation and the prospects for both sub-GeV dark-matter searches and the detection of coherent elastic neutrino-nucleus scattering. A brief discussion of the challenges associated with the construction of the foreseen detectors with multi-kilogram target mass is also presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

NASA NTRS1982

Low-background performance of a monolithic InSb CCD array

A 20 element monolithic InSb charge coupled device (CCD) detector array was measured under low background conditions to assess its potential for orbital astronomical applications. At a temperature of 64 K, previous results for charge transfer efficiency (CTE) were reproduced, and a sensitivity of about 2 x 10 to the minus 15th power joules was measured. At 27 and 6 K, extended integration times were achieved, but CTE was substantially degraded. The noise was approximately 6000 charges, which was in excess of the level where statistical fluctuations from the illumination could be detected. A telescope demonstration was performed showing that the array sensitivity and difficulty of operation were not substantially different from laboratory levels. Ways in which the device could be improved for astronomical applications were discussed.

Bregman, J. D.↗

NASA NTRS1985

Backside charging of the CCD

Until recently, the usefulness of the charge coupled device (CCD) as an imaging sensor was thought to be restricted to within rather narrow boundaries of the visible and near IR spectrum. However, since the discovery of backside charging the full potential of CCD performance is now realized. Indeed, the technique of backside charging not only allows the CCD to be used directly in the UV, EUV, and soft X-ray regimes, it has opened up new opportunities in optimizing charge collection processes as well. The technique of backside charging is discussed, and its properties, use, and potential in the future as it applies to the CCD are described.

Janesick, J.↗

DOE OSTI2020

Low Threshold Acquisition controller for Skipper CCDs

The development of the Skipper Charge Coupled Devices (Skipper-CCDs) has been a major technological breakthrough for sensing very weak ionizing particles. The sensor allows to reach the ultimate sensitivity of silicon material as a charge signal sensor by unambiguous determination of the charge signal collected by each cell or pixel, even for single electron-hole pair ionization. Extensive use of the technology was limited by the lack of specific equipment to operate the sensor at the ultimate performance. In this work a simple, single-board Skipper-CCD controller is presented, aimed for the operation of the detector in high sensitivity scientific applications. The article describes the main components and functionality of the Low Threshold Acquisition (LTA) together with experimental results when connected to a Skipper-CCD sensor. Measurements show unprecedented deep sub-electron noise of 0.039 e$^-_{rms}$/pix for 5000 pixel measurements.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

NASA NTRS2003

Chromatic Modulator for High Resolution CCD or APS Devices

A system for providing high-resolution color separation in electronic imaging. Comb drives controllably oscillate a red-green-blue (RGB) color strip filter system (or otherwise) over an electronic imaging system such as a charge-coupled device (CCD) or active pixel sensor (APS). The color filter is modulated over the imaging array at a rate three or more times the frame rate of the imaging array. In so doing, the underlying active imaging elements are then able to detect separate color-separated images, which are then combined to provide a color-accurate frame which is then recorded as the representation of the recorded image. High pixel resolution is maintained. Registration is obtained between the color strip filter and the underlying imaging array through the use of electrostatic comb drives in conjunction with a spring suspension system.

Frank T Hartley↗

DOE OSTI2025

Towards a quantum realization of the ampere using single-electron resolution Skipper-CCDs

This paper presents a proof-of-concept demonstration of the Skipper-charge coupled device (CCD), a sensor with single-electron counting capability, as a promising technology for implementing an electron-pump-based current source. Relying on its single-electron resolution and built-in charge sensing, it allows self-calibration of the charge packets. This article presents an initial discussion of the uncertainty in the charge measurement and achievable currents levels with this technology. Here, we report experimental results that illustrate the key functionalities in manipulating both small and large electron charge packets, including a comparison of the charge generated, self-measured, and drained by the sensor against measurements from an electrometer. These results were obtained using a standard sensor and readout electronics without specific optimizations for this application. The objective is to explore the potential of Skipper-CCD for realizing an electron-based current source.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2020

Characterization of skipper CCDs for cosmological applications

We characterize the response of a novel 250 µm thick, fully-depleted Skipper Charged-Coupled Device (CCD) to visible/near-infrared light with a focus on potential applications for astronomical observations. We achieve stable, single-electron resolution with readout noise σ 0.18 e - rms/pix from 400 non-destructive measurements of the charge in each pixel. We verify that the gain derived from photon transfer curve measurements agrees with the gain calculated from the quantized charge of individual electrons to within < 1%. We also perform relative quantum efficiency measurements and demonstrate high relative quantum efficiency at optical/near- infrared wavelengths, as is expected for a thick, fully depleted detector. Finally, we demonstrate the ability to perform multiple non-destructive measurements and achieve sub-electron readout noise over configurable sub- regions of the detector. This work is the first step toward demonstrating the utility of Skipper CCDs for future astronomical and cosmological applications.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

NASA NTRS1994

Instrumentation for X-ray Astronomy

Less than five decades ago, the first X-ray observations of the sky were made using simple devices such as film and geiger counters with crude collimators. These instruments were carried aloft by sounding rockets and made observations lasting only a few minutes at most. Today, orbiting observatories, utilizing high-resolution charged coupled devices (CCD's) at the focus of arc sec optics, have lifetimes measured in years. To maintain the pace of discovery in X-ray astronomy, detectors must continue to evolve into devices of ever increasing sensitivity and sophistication. Further progress depends upon a host of technologies: grazing incidence optics, proportional counters, semiconductors, calorimeters, etc. In this article we present a brief qualitative overview of these technologies and of the principles behind them, as well as some examples of how they are employed in scientific missions for X-ray observations at energies up to 100 keV.

Ramsey, Brian D.↗